Question

Difficulty: Very hardAlgebraic Word Problems and Equation Modeling

A private equity firm invested a total of $1,000,000\$1,000,000 divided between two portfolio companies, Company A and Company B. During the first year, the value of Company A increased by x%x\%, while the value of Company B decreased by x%x\%, where x>0x > 0. At the end of the first year, the value of Company A was $720,000\$720,000, and the combined value of both companies was $1,040,000\$1,040,000. If the value of Company B decreased by an additional x%x\% during the second year relative to its value at the end of the first year, what was the value, in dollars, of Company B at the end of the second year?

Answer: 256000 dollars

Answer

The value of Company B at the end of the second year was 256,000 dollars.
By representing the initial investments as algebraic expressions involving the multiplier k=x100k = \frac{x}{100} and setting up the total initial capital equation A0+B0=1,000,000A_0 + B_0 = 1,000,000, we obtain a quadratic equation in kk. Solving (5k1)2=0(5k-1)^2 = 0 yields k=0.2k = 0.2 (x=20%x = 20\%). Decreasing Company B's Year 1 value of $320,000\$320,000 by 20%20\% gives $256,000\$256,000.

Step-by-Step Solution

1
Find the value of Company B at the end of Year 1
Year 1 value of Company B = 1,040,000720,000=320,0001,040,000 - 720,000 = 320,000 dollars
The total combined value of both companies at the end of Year 1 is given as $1,040,000.
2
Formulate algebraic expressions for initial values using rate k=x100k = \frac{x}{100}
A0=720,0001+kA_0 = \frac{720,000}{1+k} and B0=320,0001kB_0 = \frac{320,000}{1-k}
Company A increased by x%x\% so A1=A0(1+k)A_1 = A_0(1+k); Company B decreased by x%x\% so B1=B0(1k)B_1 = B_0(1-k).
3
Set up and simplify the quadratic equation for the combined initial investment
720,0001+k+320,0001k=1,000,000    25k210k+1=0\frac{720,000}{1+k} + \frac{320,000}{1-k} = 1,000,000 \implies 25k^2 - 10k + 1 = 0
Dividing by 80,00080,000 yields 91+k+41k=12.5\frac{9}{1+k} + \frac{4}{1-k} = 12.5. Multiplying through by 2(1k2)2(1-k^2) leads to 2[9(1k)+4(1+k)]=25(1k2)2[9(1-k) + 4(1+k)] = 25(1-k^2).
4
Solve for kk and determine percentage xx
(5k1)2=0    k=0.2(5k - 1)^2 = 0 \implies k = 0.2, so x=20%x = 20\%
Factoring the perfect square quadratic expression gives a unique solution for kk.
5
Compute Company B's value at the end of Year 2
320,000×(10.2)=256,000320,000 \times (1 - 0.2) = 256,000 dollars
Company B's value decreases by an additional 20%20\% of its Year 1 value (320,000320,000).

Key Concept

Algebraic Modeling of Rational/Quadratic Equations from Multi-Step Percent Change Scenarios
Estimated Time:2m 30s
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